<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin:0px;
            padding: 0px;
        }
    </style>
</head>
<body>
    <div>

    </div>

    <script>
        var div=document.querySelector("div")
        // div.style='width:100px;height:100px;background:red';

        //style本身也是对象
        //style属性是没有横线的，后面的首字母大写(驼峰命名法)
        div.style.width='500px';
        div.style.height='500px'
        div.style.backgroundColor='red'
        div.style.marginLeft='100px'
        div.style.borderRadius='20px'
        div.style.border='5px solid blue'
        div.style.borderLeftStyle='dashed' // 虚线
    </script>
    
</body>
</html>